Published online by Cambridge University Press: 18 July 2011
The Chilean hake (Merluccius gayi gayi) is the predominant groundfishspecies inhabiting the southern Humboldt, mainly from Coquimbo (29° S) to Puerto Montt(42° S). At present there is only limited knowledge on the spatial distribution ofjuveniles of this species, particularly concerning its dependence on key physicalcharacteristics. On the basis of annual surveys carried out during austral winters from1997 to 2006, changes in the presence of juveniles were studied using Generalized AdditiveModel techniques. Temporal factors and spatial effects were more important than singlephysical variables in explaining the presence of juvenile hake (<34 cm totallength). Juvenile hake had a preference for shallower waters. Although salinity and oxygenwere significant, their contribution was marginal. Juvenile hake seem to prefer shallowoxygenated waters, but the nonlinear relationships and partial secondary peaks detected insalinity and oxygen probably only reflected the influence of three water masses found inthe winter habitat. Endogenous factors could be more important in determining temporal andspatial changes in the proportion of juvenile hake. An important change in the presence ofjuveniles has occurred since 2004, coinciding with a significant decline in biomass ofadult hake. It is postulated that cannibalism pressure from adults has probably declinedand that spatial and temporal changes in the presence of juvenile hake seem to be moreassociated with fishery-induced demographic effects.